The present invention relates to a method and apparatus for controlling the load placed on a compressor and, more particularly, the load placed on a compressor used with a refrigerated cabinet.
Refrigerated cabinets and the refrigeration systems which cool such refrigerated cabinets experience variable load conditions. The variable load conditions may occur due to a temperature increase of the contents of the refrigerator, such as when warm objects are placed in the refrigerator. Further, changes in the temperature of the ambient environment or frequency and duration at which users access the refrigerated cabinet will also vary the cooling load placed on the refrigeration system.
Refrigerated cabinets, as may be found in grocery stores or used as vending machines for cooled products, may employ a Complete Refrigeration System (“CRS”) that is constructed as a module and provides the refrigeration system for cooling the cabinet. The CRS modules can be readily installed and removed from a refrigerated cabinet whereby such modules are interchangeable and easily serviced.
Typically, the compressor used with a refrigerated cabinet, such as in a CRS installed in the cabinet, is selected to have a capacity that is sufficient meet the expected peak cooling load of the refrigerated cabinet. For example, vending machines must often cool products from an ambient temperature to a predetermined storage temperature within a predetermined time period. The initial cooling load generated by loading a vending machine with ambient temperature products can be relatively significant. Oftentimes, the compressor for such vending machines is selected on the basis of whether the maximum rated capacity of the compressor is sufficient to meet the maximum load that such a vending machine would experience when it is fully loaded with ambient temperature products. When the compressor is selected on this basis, the compressor will often be larger than necessary for the loading conditions most frequently experienced by the vending machine and the efficiency of the compressor will be less than optimal.